title: Contribution of corticospinal tract and functional connectivity in hand motor impairment after stroke.
abstract: BACKGROUND
  Motor outcome after stroke is associated with reorganisation of cortical networks and corticospinal tract (CST) integrity. However, the relationships between motor severity, CST damage, and functional brain connectivity are not well understood. Here, the main objective was to study the effect of CST damage on the relationship between functional motor network connectivity and hand motor function in two groups of stroke patients: the severely (n=8) and the mildly impaired (n=14).
  
  
  METHODS
  Twenty-two carotid stroke patients with motor deficits were studied with magnetic resonance imaging (MRI) at 3 weeks, at 3 and 6 months. Healthy subjects (n=28) were scanned once. The CST injury was assessed by fractional anisotropy values. Functional connectivity was studied from a whole-hand grip task fMRI in a cortical and cerebellar motor network. Functional connectivity indexes were computed between these regions at each time point. The relationship between hand motor strength, ipsilesional CST damage and functional connectivity from the primary motor cortex (M1) was investigated using global and partial correlations.
  
  
  RESULTS
  In mildly impaired patients, cortico-cortical connectivity was disturbed at three weeks but returned to a normal pattern after 3 months. Cortico-cerebellar connectivity was still decreased at 6 months. In severely impaired patients, the cortico-cortical connectivity tended to return to a normal pattern, but the cortico-cerebellar connectivity was totally abolished during the follow-up. In the entire group of patients, the hand motor strength was correlated to the ipsilesional functional connectivity from M1. Partial correlations revealed that these associations were not anymore significant when the impact of CST damage was removed, except for the ipsilesional M1-contralateral cerebellum connectivity.
  
  
  CONCLUSIONS
  Functional brain connectivity changes can be observed, even in severely impaired patients with no recovery. Upper limb function is mainly explained by the CST damage and by the ipsilesional cortico-cerebellar connectivity.
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière (CRICM), Université Pierre et Marie Curie, Paris, France ; Inserm, U975; CNRS, UMR 7225, Paris, France ; COGIMAGE, CRICM, Paris, France ; APHP, Urgences Cérébro-Vasculaires, Hôpital Pitié-Salpêtrière, Paris, France ; IFR49, DSV/I2BM/NeuroSpin, Université Paris 11, Gif-sur-yvette, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Rosso
authors.forename: Romain
authors.initials: R
authors.lastname: Valabregue
authors.forename: Yohan
authors.initials: Y
authors.lastname: Attal
authors.forename: Patricia
authors.initials: P
authors.lastname: Vargas
authors.forename: Marie
authors.initials: M
authors.lastname: Gaudron
authors.forename: Flore
authors.initials: F
authors.lastname: Baronnet
authors.forename: Eric
authors.initials: E
authors.lastname: Bertasi
authors.forename: Frédéric
authors.initials: F
authors.lastname: Humbert
authors.forename: Anne
authors.initials: A
authors.lastname: Peskine
authors.forename: Vincent
authors.initials: V
authors.lastname: Perlbarg
authors.forename: Habib
authors.initials: H
authors.lastname: Benali
authors.forename: Stéphane
authors.initials: S
authors.lastname: Lehéricy
authors.forename: Yves
authors.initials: Y
authors.lastname: Samson
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002339:Carotid Arteries / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D006225:Hand / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D011446:Prospective Studies; D013116:Spinal Cord / Q000503:physiopathology*; D020521:Stroke / Q000503:physiopathology*